Around 100,000 miles of disused dry stone walls in New England (US) have slowly been taken over by reforestation after farm and industrial land was abandoned at the end of the 19th century. Read the full Atlas Obscura article here which finishes with:
Each of the millions of stones that make up New England stone walls was held by a person, usually a subsistence farmer, or perhaps a hired Native American or a slave. What remains is a trace of countless individual acts etched on the landscape.